Low level radioactivity measurement in support of the CTBTO

Radioactivity measurements, together with three other technologies: seismic, hydroacoustic and infrasound, are able to detect, identify and locate nuclear explosions down to 1 kt. Eighty stations worldwide, with a sensitivity of 10–30 μBq/m3 for 140Ba and 1 mBq/m m3 for 133Xe, have been or will be established in order to provide an estimated 90% detection probability within 10 days after a nuclear explosion. The equipment for manual stations — the high volume samplers, high sensitivity HPGe detectors and auxiliary measurement systems, as well as the automatic stations are described. The problems and results of atmospheric transport, site location as well as equipment and station operation are discussed.